1. Field of the Invention
The present invention relates, in general, to piezo valves and, more particularly, to a piezo valve having a piezo plate actuated by an electric voltage.
Particularly, the present invention relates to a piezo valve in which a piezo plate is fastened by a method different from those used in conventional piezo valves, thus having an improved performance.
2. Description of the Related Art
Generally, a piezo valve opens or closes a flow path using a piezo plate bending-strained by an electric voltage. In recent years, these piezo valves are installed in vehicles and control the supply of engine fuel or control the supply of air for airbags embedded in the backs of passenger seats.
FIG. 1 is a sectional view illustrating the construction of a conventional piezo valve. In the conventional piezo valve, a piezo plate 7 is installed in a casing 2, as shown in FIG. 1, and is bending-strained at a first end thereof by an electric voltage applied thereto and opens or closes valve seats 4A and 5A of the casing 2. The piezo valve may be configured to open or close the two valve seats 4A and 5A of the casing 2, as shown in FIG. 1, or may be configured to open or close only one of the two valve seats 4A and 5A unlike the embodiment shown in the drawing.
In the piezo valve, the second end of the piezo plate 7 may be fastened to the casing 2 using a rubber plate 8, as shown in FIG. 1, or may be fastened to the casing 2 using epoxy mixed with a hardening agent.
However, because the piezo plate 7 of the piezo valve is fastened to the casing 2 at the second end thereof using the rubber plate 8 or the epoxy mixed with the hardening agent, it is very difficult to fasten the piezo plate 7 to the casing and it is impossible to adjust the fastened position of the piezo plate 7.
Further, because the first end of the piezo plate 7 directly opens or closes the valve seats 4A and 5A, the conventional piezo valve is problematic in that it has low sealing effect and low precision.
Therefore, in recent years, in an effort to increase both the sealing effects and the precision of the piezo valve, a piezo valve, in which a rubber valve disc is attached to the first end of the piezo plate 7 using a bonding agent, has been proposed. However, in the piezo valve, the rubber valve disc is directly attached to the first end of the piezo plate 7 using the bonding agent, so that the properties of the bending-strained end of the piezo plate 7 may be reduced or the end of the piezo plate 7 may be twisted, thereby reducing the valve performance of the piezo valve or reducing the precision of the piezo valve.
In recent years, a piezo valve having both a circuit board (not shown) and a pressure sensor (not shown) in the casing 2 has been marketed. The piezo valve is advantageous in that an electric voltage is applied to the piezo plate 7 through the circuit board and the pressure inside the casing 2 can be detected by the pressure sensor. However, the piezo valve is problematic in that a fluid passes both by the circuit board and by the pressure sensor, and that the fluid shortens the life spans of the circuit board and the pressure sensor and the piezo valve cannot realize precise control of the flow of a liquid fluid.